The present invention relates to a device for fixation of bone fragments at bone fractures. The device comprises at least two fixation means and a securing plate.
After a bone fracture such as a femur neck fracture, the bone fragments at the fracture need fixing. This is currently done by using suitable fixation means, e.g. bone nails or bone screws.
After the completion of surgery, even as early as when the effects of the anaesthesia have passed and the patient is still confined to bed, but above all when the patient is beginning to be up and walk and stand on the leg, the fixed bone fragments and the fixation means are subject to large forces, particularly to rotational forces downwards and rearwards.
The fixation means alone are often insufficient to counteract these rotational forces and the bone fragments have to be used to help to lock the fracture. If this is not done and the bone fragments are caused to rotate relative to one another by said forces, the result rill be shifting of the angular positions of the fixation means to such an extent that they risk substantially crossing one another, thereby keeping the fracture parted and preventing healing.
The object of the present invention is accordingly to prevent ear counteract this and therefore configure the device in such a way that the fixation means are not allowed to rotate and cross one another.
To this end, with the device according to the invention, each fixation means has a first fixing portion for fixing the fixation means in an inner bone fragment, a second fixing portion for locking the fixation means to the securing plate disposed on the outside of an outer bone fragment and allowing movement if the outer bone fragment relative to it, so that the fixation means are prevented from changing their angular position relative to the securing plate and relative to one another, and a middle portion which is situated between the fixing portions and runs through the outer bone fragment, along which middle portion the outer bone fragment can slide inwards towards the inner bone fragment in which the fixation means is fixed.
The result of the fixation means being thus fixed to the inner bone fragment and to the securing plate while the outer bone fragment can move towards the inner bone fragment and, in so doing, be guided by the fixation means is that the bone fragments are kept fixed but compression of the bone fragments is nevertheless allowed, the device and the bone fragments thus being able to absorb the aforesaid rotational forces and control them so that no re-dislocation occurs. The fixing of the fixation means in the inner bone fragment and the locking of the fixation means to the securing plate also reduce the risk of screws loosening in cases where the fixation means take the form of bone screws.)